1. Field of the Invention
The present invention relates to a multi-level circuit substrate having interlayer connection through a conductor filled between layers thereof, a method for manufacturing same and a method for adjusting a characteristic impedance therefor.
2. Description of the Related Art
Recently there has been an increasing demand for implementing high density mounting of semiconductor devices with increase in the need to enhance operation speed and improve performances for the computers. In the high end field of super-computers, etc., the ceramic substrate utilized in semiconductor device mounting is structured by two interconnect layers sandwiched between ground layers (or power source layers). This have realized reduction of cross talk and control of characteristic impedance together with high density mounting. For data transfer utilizing a high clock frequency, however, the adoption of such a structure cannot provide for sufficient effects to reduce cross talk and control characteristic impedance.
Under such a situation, in conventional there has been a technology disclosed in a publication of Japanese Patent Laid-open No. 206678/1993. In this technology, five or more shield connection members are provided for a multi-level substrate having a shield connection member around a signal connection member thereof. Due to this, the reduction of cross talk and stabilization of characteristic impedance are achieved at around interlayer connecting portions. However, such a structure requires many connection members for the interconnect substrate. Thus, there is insufficiency in compatibility with today's high density mounting and increase in number of pins.